Mix vessels are the foundation of every liquid processing operation, and rely on several systems working cohesively together. When properly designed, engineered, manufactured and maintained, the components of a mix tank will boost efficiency and deliver a consistent product for years, or even decades. Choosing the right system for your specific operation is key, and there are many considerations that are pivotal.
At Mixing Tanks USA, we’ve taken real-world use and experience to create a practical guide for engineers, operators, and business owners as they consider adding capacity or upgrading legacy equipment. We’ve found again and again that these seven steps produce better decisions and outcomes.
Step 1: Know Your Game: What Exactly are You Mixing
The biggest mistakes we see in choosing a tank is basing decisions on legacy engineering standards instead of evaluating the fundamentals of what you intend to mix.
Before size or price, it’s important to answer a few basic process questions:
- What are you mixing? (liquid–liquid, solid–liquid, slurry, paste, high-viscosity),
- Are your ingredients explosive, corrosive, or do they off gas?
- What viscosity range do you expect during the batch and do you anticipate that changing?
- Are your products Newtonian or shear-sensitive?
- Do ingredients change during mixing (hydration, heating, reaction)?
- Do you intend to run batch or continuous operation or a hybrid of the two?
- Do you need redundancy, and how much redundancy is critical for efficiency, maximized throughput, and product consistency?
A clear understanding of your products, how they behave and how you intend to maximize efficiency in the future helps to determine next steps.
Step 2: Design Tank Sizes and Aspect Ratios to Maximize Efficiency
Tank sizing is about more than total volume. Variation in batch chemistry and production demand may be bigger factors in determining your tank sizes than the amount of product you make in a single batch. To avoid making your liquid production process a bottleneck, think in terms of throughput that is smooth, consistent, and timely. Tank sizing is the second step in making sure your flow is consistent. Some factors that will help determine the optimal tank size are:
Working volume vs total volume
Volume is a fundamental consideration. Process tanks should not be filled to 100%. Headspace matters for mixing, foaming, heating, and safety. Typically tanks should have from between 20% and 40% headspace.
Number of products to be formulated, and at what interval
Regardless of whether you have several products or just one, consider that a tank is only able to process one recipe at a time. If that tank is in process nothing happens downstream until its process is completed, the tank cleaned, refilled and processed again. Two process tanks at 50% of the size of a single large tank may be the answer to consistent production flow. Will multiple smaller tanks add process efficiency, redundancy and speed that you are looking for?
Current demand vs. future expansion
Are you sizing for today’s batch or tomorrow’s throughput demand? A properly sized tank, or liquid process system should allow you to operate for 3-5 years without needing to expand. A flexible system will, ideally, allow you to expand in such a way that the equipment you buy today fits seamlessly into the expanded process. Starting over is never desirable when making significant capital investments.
Aspect ratio (diameter vs height)
Tall, narrow tanks behave very differently than wide, shallow tanks. Ideally a 1:1 to 1.20:1 aspect ratio (sidewall height to diameter) is preferred. Often ceiling heights or floorspace become critical factors that short circuit best design practices. In those cases mix design, heating and cooling need to be carefully evaluated in order to assure the entire mix tank works optimally.
Don’t Assume Bigger is Better
In many cases, customers simply oversize tanks “just to be safe,” then struggle with poor mixing, long batch times, or dead zones. A properly sized tank improves efficiency and reduces operating costs. Breaking a large vessel into smaller batch sizes increases throughput and reduces operational risk by providing redundancy.
Step 3: Choose the Right Mixer and Impeller
This is a topic of its own and will be discussed in a subsequent article. In general terms, the mixer and impeller are the muscle of the mixing tank and must be designed as part of the overall tank assembly to yield optimal mixing. In general terms the following criteria will determine the correct mixer power, speed and impeller design to use in your process:
The mixer power output and speed must take into account:
- Viscosity
- Flow pattern (axial vs radial)
- Solids loading
- Shear requirements.
The raw material inputs and desired consistency of the finished product will determine which impeller type to use. It’s not uncommon for two or even three mixer assemblies, with carefully selected impeller types, to work simultaneously on a single tank. The four main impeller categories are:
- Propellers for low-viscosity liquids
- Turbines for robust mixing of moderate viscosity and can be used for gas dispersion
- Anchor mixers for high-viscosity products that require wall scraping, especially used where intense cooling or heating of ingredients is required.
- High-shear mixers for emulsions and dispersion
There is no “best” impeller—only the right impeller for the application. Choosing incorrectly can lead to stalled batches, excessive motor loads, or product inconsistency.
Also, be aware that there are several hazard classes for materials that may be used in your operation. Specially designed Explosion proof (EXP) motors may be required for combustible, duty or off gassing systems. Correct EXP motor selection may not be a choice but a requirement in these environments.
Step 4: Select the Correct Material (304 vs 316 Isn’t a Guess)
Most industrial mixing tanks are stainless steel, but material selection should be intentional.
Typical considerations:
- 304 stainless steel
Suitable for many food, beverage, and industrial applications. - 316 stainless steel
Better resistance to chlorides, salts, and aggressive ingredients. - Special alloys or linings
Required for certain chemicals, solvents, or corrosive environments.
Choosing 316 “just in case” isn’t always necessary—but choosing 304 when 316 is required can be a costly mistake. Material selection should be based on chemistry, temperature, and cleaning agents. If in doubt, return to step 1.
Step 5: Cleaning Requirements Drive Design Complexity
Cleaning is often an afterthought—and then becomes the most expensive surprise. Efficient cleaning means that the cycle is rapid, repeatable, and consistently delivers the desired results.
Key questions to consider when addressing equipment cleaning are:
- Is manual cleaning acceptable, what is the cost of labor daily, monthly annually to manually clean?
- Is Clean-In-Place (CIP) required or a better option?
- Are you operating under food, beverage, or pharmaceutical guidelines that have compliance requirements or guidelines that lend themselves to automated cleaning operations?
- How often will the tank and mixer be cleaned?
Over-specifying cleaning systems adds unnecessary cost. Under-specifying them can create compliance or sanitation issues that will negatively affect throughput. Maintaining the proper level of cleaning or sanitation is certainly something that should be considered in the mixing system design.
Step 6: Heating, Cooling, and Temperature Control
If your process involves temperature changes, the tank must be designed for it. There exist specific solutions for every temperature control requirement. While we have likely encountered every use scenario, we stay informed about new technologies that enhance or change the game entirely where heat transfer is concerned.
Current state of the art heat transfer options for vessels include:
- Heat transfer jackets
- Direct injection of heating media (typically steam)
- Heat transfer internal coils
- Electric, steam, or thermal fluid heating may be employed with any of the heat transfer solutions listed above.
When assessing heating and cooling it is critical to consider the mix vessel as a system that delivers a result. The correct amount of heat, balanced with tank geometry, mixer and impeller selection combine to deliver the optimal result while avoiding a long list of less desirable outcomes.
Thermal requirements should be defined early—not added as an afterthought.
Step 7: Think in Terms of Systems, Not Components
A properly designed mixing tank is comprised of several components that work together in order to deliver exact results, and a mix tank rarely operates alone. Valves, manifolds, piping, pumps, instrumentation and integrated controls connected to your mixing vessel(s) make up a process system.
A turnkey mixing system that unloads raw materials, processes them and produces a package ready end product significantly reduces installation risk, shortens timelines, and lowers total installed costs. If you want an exact cost for installing a liquid process system, a turnkey skid-mount installation may be the best option.
The Bottom Line
The right mixing tank is not the cheapest one, the biggest one, or the one with the longest feature list. It’s the one that matches your process, product, and production reality.
At Mixing Tanks USA, we spend more time asking questions than pushing equipment—because getting it right upfront saves time, money, and frustration later.
If you’re evaluating a mixing tank or liquid process system and want a second opinion, we’re happy to talk through your application and help you avoid common pitfalls.